noisy lifters on 4.0 liter

[garysmith]

I have a cherokee with a 4.0 liter engine. I have used it for 500 miles. Tappet noise from one valve was apparent. When at freeway speeds, the noise would disappear. The problem will always occur if the engine idles or I drive city streets,

I added oil detergent when te problem was first evident. It has seemed to do no good. I check the oil level frequently.

Can I replace the tappet assembly when I pull the valve cover to correct an oil leak? Should I replace only the failing tappet? Is there a chemical solvent resolve?

Anyone share my problem?

Gary with Greyghost
:roll:

[Chris S]

Is it a new or old XJ?

Tapping on older XJs is common and is usually caused by using high octane gas. High octane gas burns slower. This results in carboning of the valves. The carbon makes the valves stick, causing the tap.

Tapping in 97-98 XJs at low revs under load is due to a poor choice of ignition timing, and can be modified by the dealer.

[satan]

Not addressed-

the head on the 4.0 will not allow the removal of the Lifters (tappets) with the head installed -- to replace the lifters, you'll need to pull the head; then I would suggest that you repkace them all (and really, a cam replacement/upgrade is not that much more of an effort...)